Hi Howard,
I could be wrong, but here goes..
The "old style" P3 telemetry decoders can only do 512 byte blocks---so you
will not be able to have a checksum check of the block (which requires the
514 bytes).
Simply put-- won't do checksum as is.
Now, what I do NOT know is if your unit is somehow modifiable/upgradeable
to do 514 byte blocks with CRC. I bet James G3RUH's site where he sells
the units/boards might comment on that?
WAIT---I just found out where the mod information is :-)
In this file are images and text describing how to do it:
http://www.amsat.org/amsat/ftp/satinfo/ao13/demod.zip
Here is an extract of one of the files
---------
Modifications to original 1984 AO-10 Data Demodulator (MK I)
--------------------------------------------------------------
The original G3RUH demodulator, issued in 1984, outputs 512 bytes per block
(i.e. CRCC bytes are discarded) and has a serial output not at true +/-12 volt
levels.
In this directory are two GIF files that depict the circuit changes you
can make to output 514 bytes/block, and add an RS232 level interface.
In addition, there are some essential component value changes that improve
the PLL performance considerably. These are:
R7 330k C10 1n hi-stab 5%
R9 150k C11 47n
R10 470k C12 4n7 hi-stab 5%
R12 330k C13 47n
R14 330k C16 10n
R17 100R VR3 50k
Note that the 4046 PLLs are very voltage sensitive, so use a 12v stabilised
supply.
James Miller G3RUH 1994 May 01
<eof>
--------------
Good luck with your mod! Let us know how it goes...
73,
Mark N8MH
At 04:29 PM 12/4/00 +0000, Howard Z wrote:
>I am using an old homebrew I think it's a G3RUH or something similar
>(can't really remember ) PSK converter from my AO13 days , Can someone
>please tell me why I receive no checksum and only receive RAW data , I
>have tried 512 and 514 bits , is my converter somehow obsolete ..
>
>Thanks
>
>Howard VE2AED
----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org